Question Video: Identifying the Definition of an Arrhenius Acid Chemistry

According to Arrhenius theory, which of the following can an acid be defined as? [A] A substance that changes the color of an aqueous solution. [B] A substance that ionizes in an aqueous solution to produce OH⁻ ions. [C] A substance that fizzes when placed into an aqueous solution. [D] A substance that dissolves any substance placed into a solution of it. [E] A substance that ionizes in an aqueous solution to produce H⁺ ions.

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Video Transcript

According to Arrhenius theory, which of the following can an acid be defined as? (A) A substance that changes the color of an aqueous solution. (B) A substance that ionizes in an aqueous solution to produce OH− ions. (C) A substance that fizzes when placed into an aqueous solution. (D) A substance that dissolves any substance placed into a solution of it. (E) A substance that ionizes in an aqueous solution to produce H+ ions.

To solve this problem, we need to carefully read through each answer choice to determine if it is an accurate definition of an acid. The definition of the acid must correspond to the Arrhenius theory of acids and bases. This theory, proposed by Swedish scientist Svante Arrhenius in 1887, focused specifically on how acids and bases ionize or dissociate into ions when dissolved in water. The result of an acid or base ionizing in water is an aqueous solution containing dissolved ions. Let’s begin examining the answer choices.

The statement in answer choice (A) describes the substance that changes the color of an aqueous solution. Arrhenius theory defines an acid based on the ability of the acid to ionize in an aqueous solution, not change the color of the solution. Because ionization is not described, answer choice (A) can be eliminated. Next, let’s take a look at answer choice (C). This statement describes a substance that fizzes when placed into an aqueous solution. The Arrhenius definition of an acid must include how an acid ionizes when dissolved in water. Because ionization is not described, answer choice (C) can also be eliminated.

The statement in answer choice (D) describes a substance in a solution that will dissolve any substance placed into it. It’s important to recognize that Arrhenius theory is focused on what happens when an acid dissolves in water, not what happens when substances are dissolved in an acidic solution. We can eliminate answer choice (D) for this reason. And there are plenty of examples of substances that will not dissolve in an acidic solution.

The only answer choices left our answer choices (B) and (E). Both of these answer choices describe a substance that ionizes in an aqueous solution, but only one of them is correct. The substance in answer choice (B) produces OH− ions when it ionizes in the solution. This statement is the definition of a base according to Arrhenius theory. An example of an Arrhenius base is potassium hydroxide or KOH. When solid potassium hydroxide dissolves in water, it ionizes to produce K+ and OH− ions in the solution. We can eliminate answer choice (B) because the statement is the definition of a base.

Finally, answer choice (E) describes a substance that ionizes in an aqueous solution to produce H+ ions. This statement is the definition of an acid according to the Arrhenius theory. An example of an Arrhenius acid is hydrobromic acid or HBr. When dissolved in an aqueous solution, hydrobromic acid molecules ionize to produce H+ and Br− ions. The hydrogen ions produced are then accepted by water molecules in the aqueous solution forming H3O+ or hydronium ions.

The statement that defines an acid according to the Arrhenius theory is answer choice (E), a substance that ionizes in an aqueous solution to produce H+ ions.

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